A HYBRID FLOTATION – MICROFILTRATION CELL FOR METAL IONS RECOVERY E.N. Peleka, * N.K. Lazaridis, P. Mavros, D. Zamboulis and K.A. Matis Section of Chemical Technology & Industrial Chemistry, School of Chemistry, Aristotle University, GR-54124 Thessaloniki, Greece Air bubbling, used to limit membranes fouling, could be meanwhile used under appropriate conditions as the transport means of flotation; the latter is another efficient separation technique applied in water treatment. The advantages of the combination of these two processes, i.e., flotation and membrane filtration, were utilized in a hybrid cell, and were found to work satisfactorily for solids removal and producing a clean aqueous stream. In the present work, metal ion (copper) recovery was investigated, applying various flotation techniques. Keywords: hybrid system, microfiltration, flotation, wastewater treatment INTRODUCTION Dissolved heavy metals escaping into the environment pose a serious health hazard. A wide variety of metal-bearing waste streams require treatment. Mines and mineral processing plants are often operating on a totally closed water circuit as far as process effluents are concerned. Nevertheless, they are situated sometimes in or close to water-catchment areas (mountain slopes), and environmental action plans are required to limit acid drainage and prevent pollution, with two goals in mind: a) to remove from the aqueous effluent any undesirable dissolved or even suspended constituents, and/or b) to recover a stream of water clean enough for potential re-use. Various processes are available for these goals. Flotation is the typical separation process for the removal of suspended matter from solutions; it is widely applied for systems involving organic components, metal ions, oils, powders, and residual reagents from wastewater (see, among others, Matis, 1995, and Rubio et al., 2002). Depending upon the specific mechanisms of the process, which depend upon the type of particle or species to be removed, several sub- processes have been devised: sorptive, precipitate and adsorbing colloid flotation (Lazaridis et al., 2004). On the other hand, membrane filtration is another process used in water and wastewater treatment. Membranes are semi-permeable materials, allowing the selective passage of certain species, while obstructing the passage of others. Using an appropriate membrane, it is possible to control the type and the amount of dissolved or dispersed species passing though them, resulting in two separate streams, one of which may be practically free of the undesirable components. The objective of the present paper is to present results obtained with a hybrid cell combining the two aforementioned processes, i.e., flotation and membrane filtration, into a single process vessel. The combined process was applied to: * E-mail: peleka@chem.auth.gr